# GHSA-2mjx-qc3c-rqvc: Rustls: TLS 1.3 handshake messages incorrectly accepted across encryption level boundaries


- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Fix available:** Yes
- **Published:** 14 Sep 2026
- **Also known as:** RUSTSEC-2026-0285

## What is GHSA-2mjx-qc3c-rqvc?

GHSA-2mjx-qc3c-rqvc is a vulnerability in rustls, published on 14 Sep 2026. 

### Official description

Rustls accepted TLS 1.3 handshake messages sent at the wrong encryption level when they followed a key-changing message in the same record. The handshake transcript is still authenticated, so a network-position attacker cannot use this to alter or complete a handshake; the practical effect is that a peer could send handshake messages that should be encrypted in plaintext without rustls rejecting the connection.

This issue affects rustls versions 0.23.13 through 0.23.44 inclusive.

# Original report
### Summary
Rustls (tested version 0.23.44, and it appears still an issue on latest master though I have not tested this) accepts a TLS 1.3 server flight where a plaintext EncryptedExtensions is packed into the same record as the ServerHello.

This is very similar to Go's CVE-2025-61730 fixed in https://github.com/golang/go/commit/5046bdf8a612b35a2c1a9e168054c1d5c65e7dd7

### Details
It appears `Deframer::aligned` considers itself aligned as long as all messages remaining in the buffer are complete. Rustls processes the ServerHello, installs the handshake keys, then pulls the complete (plaintext) EncryptedExtensions out of the buffer.

This is insufficient per RFC 8446 section 5.1's

> Handshake messages MUST NOT span key changes.  Implementations MUST verify that all messages immediately preceding a key change align with a record boundary; if not, then they MUST terminate the connection with an "unexpected_message" alert.  Because the ClientHello, EndOfEarlyData, ServerHello, Finished, and KeyUpdate messages can immediately precede a key change, implementations MUST send these messages in alignment with a record boundary.

### Impact
An on path attacker can inject plaintext messages that are accepted.

### Tool Use Disclosure
This was discovered by a new TLS/DTLS test suite currently under construction. The specific testcase was inspired by the Go CVE. Other tested implementations (Botan, OpenSSL, BoringSSL, Go, wolfSSL) reject this protocol flow. Daybreak Blue reviewed the rustls code to identify probable root cause.

## Which versions are affected by GHSA-2mjx-qc3c-rqvc?

3 open source packages ship an affected version, including rustls.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `rustls` | crates.io | From 0.23.13 | 0.23.45 |
| `rustls` | crates.io | From 0.23.13 | 0.23.45 |
| `rustls` | crates.io | From 0.23.13 | 0.23.45 |

## How do I fix GHSA-2mjx-qc3c-rqvc?

Upgrade rustls to 0.23.45 or later.

## Is GHSA-2mjx-qc3c-rqvc being exploited?

There is no known exploitation of GHSA-2mjx-qc3c-rqvc in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for GHSA-2mjx-qc3c-rqvc and fix it if it is affected.

What it is: GHSA-2mjx-qc3c-rqvc is a vulnerability in rustls, published on 14 Sep 2026. 
Exploitation: There is no known exploitation of GHSA-2mjx-qc3c-rqvc in the wild and no public exploit code.

Affected packages and fixed versions:
- rustls (crates.io): affected from 0.23.13; fixed in 0.23.45
- rustls (crates.io): affected from 0.23.13; fixed in 0.23.45
- rustls (crates.io): affected from 0.23.13; fixed in 0.23.45

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/GHSA-2mjx-qc3c-rqvc/ (Markdown: https://insights.sbomify.com/GHSA-2mjx-qc3c-rqvc/index.md)
```

## Sources

- OSV: https://osv.dev/vulnerability/GHSA-2mjx-qc3c-rqvc

---
From sbomify Insights: https://insights.sbomify.com/GHSA-2mjx-qc3c-rqvc/
Summaries are generated and may contain mistakes; the official description above is the record.